I try to be a proper web citizen and use rel=canonical (and it’s counterpart, rel=syndication) for content that has been published elsewhere. As a result, I have many HTML pages on my HTTPS-enabled domain that “link” to HTTP content.

This is leading to many “insecure mixed content” warnings in post-processing.

As I understand mixed content, this risk is only relevant to resources a browser will load. So I believe Netlify is being too aggressive in treating all <link> href attributes as content for this test.